This invention relates to locking mechanisms for use with an overhead door, in particular with the type of overhead door on which supporting rollers move up or down in a vertical track or rail. The locking mechanism provides a bar or rod that passes into the path of the rollers in the track, and obstructs the roller from movement in the direction to open the door. The locking mechanism is a straightforward mechanical item with a frame, bar, spring, and a place to secure a padlock to hold the mechanism in its locked position. A microswitch contained within the housing changes state (from open or OFF to closed or ON) when the locking mechanism is moved to the locked position. The microswitch can be used to indicate the locked/unlocked status of the overhead door, and may also be used as an interlock, e.g., to prevent a hydraulic dock leveler from actuating when the door is closed and locked, or to keep a dock light from turning on, which might heat a spot on the door and cause heat damage.
To date, overhead door locks of this kind have been made of a sheet steel bent into a box shape which is mounted onto the door, with a bar that slides through slots in the box, and which enters a slot cut in the track or rail. These devices are prone to bending and deforming, and are often damaged after a period of normal use in an industrial or warehouse environment. Consequently, there is a need for frequent replacement. Also, the security afforded by these conventional overhead door locks is quite limited.
An example of a lock for an overhead door is described in Shoemaker U.S. Pat. No. 6,027,148 in which a fixed component mounted onto the frame of the overhead door, i.e., somewhere along the track, captures a rod that is mounted somewhere on the movable overhead door, entering an opening in a rotary element that turns and is retained in a detent. This is a fairly complex apparatus, with numerous moving parts which can be easily knocked out of alignment.
Another example of a lock for an overhead door is described in Shoemaker Patent Application Publication Pub. No. 2003/0188489, in which a rocking member, e.g., a cam, is disposed in a trackway of the overhead door, allowing the door to close but blocking a track wheel to prevent opening until the cam is moved out of the way. This device automatically moves the cam to the closed position, and a solenoid needs to be actuated to release the cam to permit the overhead door to open.